As someone who loves making ramen at home, and judging entirely from a photo which speaks nothing of taste, it might be a little miso heavy. If you live in a western country, using chicken stock to dilute it should be perfectly fine.
Thanks! Getting the amount of tare right is still something I'm working on, and it's fun to experiment with different ones. This is made with red miso, which also makes the color a bit stronger than with white miso.
That’s probably the easiest part. You hard boil eggs and then let them sit in a mix of mirin, soy sauce, and sugar. Some recipes add more ingredients to the marinade, but that’s the basic version. They can marinate for between 3 days to a week.
6.5 to 7 minutes depending on the size of your eggs. For flavouring, it's a general stock of ginger, soy, mirin, sugar which I recommend looking up and trying various blends for what you like best